Pentachlorophenol

87-86-5

Hazard Summary-Created in April 1992; Revised in January 2000

Pentachlorophenol was once one of the most widely used biocides in the
United States, but it is now a restricted use pesticide and is no longer
available to the general public. It was primarily used as a wood
preservative. Pentachlorophenol is extremely toxic to humans from
acute (short-term) ingestion and inhalation exposure. Acute inhalation
exposures in humans have resulted in neurological, blood, and liver effects,
and eye irritation. Chronic (long-term) exposure to pentachlorophenol
by inhalation in humans has resulted in effects on the respiratory tract,
blood, kidney, liver, immune system, eyes, nose, and skin. Human
studies are inconclusive regarding pentachlorophenol exposure and reproductive
effects. Human studies suggest an association between exposure to
pentachlorophenol and cancer. Oral animal studies have reported
increases in liver tumors and two uncommon tumor types. EPA has
classified pentachlorophenol as a Group B2, probable human carcinogen.

Please Note: The main sources of information for this fact sheet are
EPA's Integrated Risk Information System (IRIS), which
contains information on oral chronic toxicity of pentachlorophenol and
the RfD and the carcinogenic
effects of pentachlorophenol including the unit cancer risk for oral exposure,
and the Agency for Toxic Substances and Disease Registry's (ATSDR's) Toxicological
Profile for Pentachlorophenol.

Uses

Pentachlorophenol was once one of the most widely used biocides in
the United States, but it is now a restricted use pesticide and is no
longer available to the general public. (1)

The principal use for pentachlorophenol is as a wood preservative;
it is also used for the formulation of fungicidal and insecticidal solutions
and for incorporation into other pesticide products. (1)

Sources and Potential Exposure

Exposure to pentachlorophenol in the indoor air of pressure-treated
log homes brushed with pentachlorophenol has been measured at 0.0005
to 0.01 parts per billion (ppb), and levels in the air of industrially
dipped, non-pressure-treated log homes have been measured at 0.034 to
0.0104 ppb. Levels in outdoor air are much lower, and the general
population is estimated to breathe in about 0.063 milligrams per day
(mg/day). (1)

Workers at wood treatment facilities and lumber mills are estimated
to breathe in about 10.5 to 154 mg/day, and workers who handle treated
lumber can absorb about 35 mg/day through the skin. (1)

Pentachlorophenol has been detected at low levels in drinking water
and food. (1)

Exposure may also occur through dermal contact with pentachlorophenol
or with wood products treated with pentachlorophenol. (1)

Assessing Personal Exposure

Pentachlorophenol and its breakdown products can be measured in blood,
urine, and tissues. (1)

Tests involving acute exposure of rats and mice have shown pentachlorophenol
to have high toxicity from inhalation
exposure and extreme toxicity from
oral exposure. (1,4)

Chronic Effects(Noncancer):

Chronic exposure by inhalation to pentachlorophenol in humans has
resulted in inflammation of the upper respiratory tract and bronchitis,
blood effects such as aplastic anemia, effects on the kidney and liver,
immunological effects, and irritation of the eyes, nose, and skin. (1,3)

Chronic oral exposure to pentachlorophenol in animals has resulted
in effects on the liver, kidney, blood, endocrine, immune system, and
CNS. (1,2,5)

EPA has not established a Reference Concentration (RfC)
for pentachlorophenol. (2)

The Reference Dose (RfD)
for pentachlorophenol is 0.03 milligrams per kilogram body weight per
day (mg/kg/d) based on liver and kidney pathology in rats. The RfD
is an estimate (with uncertainty spanning perhaps an order of magnitude)
of a daily oral exposure to the human population (including sensitive
subgroups) that is likely to be without appreciable risk of deleterious
noncancer effects during a lifetime. It is not a direct estimator
of risk but rather a reference point to gauge the potential effects.
At exposures increasingly greater than the RfD,
the potential for adverse health effects increases. Lifetime exposure
above the RfD does not imply
that an adverse health effect would necessarily occur. (2)

EPA has high confidence in the study on which the RfD
is based because a moderate number of animals/sex were used in each
of three doses, a comprehensive analysis of parameters was conducted,
and a reproductive study was also performed; medium confidence in the
supporting database because only one chronic study is available; and,
consequently, medium confidence in the RfD.
(2)

One study reported that 22 out of 90 women with histories of spontaneous
abortions, unexplained infertility, or menstrual disorders were found
to have elevated blood levels of pentachlorophenol and/or lindane.
However, a direct causal relationship with pentachlorophenol exposure
cannot be inferred from this study due to the presence of lindane in
the blood and other possible confounding factors. (1)

Oral animal studies suggest that exposure to pentachlorophenol decreases
the survival of the offspring in rats. Other oral animal studies
have found evidence that pentachlorophenol produces maternal toxicity
(depressed maternal body weight), but does not cause birth defects.
(1,2)

Cancer Risk:

Case reports suggest a possible association between inhalation pentachlorophenol
exposure and cancer (Hodgkins disease, soft tissue sarcoma, and acute
leukemia); however, concommittent exposure to other toxic substances
may have contributed to the reported carcinogenic effects. (1)

EPA has classified pentachlorophenol as a Group B2, probable human
carcinogen. (2)

EPA uses mathematical models, based on animal studies, to estimate
the probability of a person developing cancer from ingesting water containing
a specified concentration of a chemical. EPA calculated an oral unit
risk estimate of 3 × 10-6 (µg/L)-1.
EPA estimates that, if an individual were to ingest water containing
pentachlorophenol at an average concentration of 0.3 µg/L over
his or her entire lifetime, that person would theoretically have no
more than a one-in-a-million increased chance of developing cancer as
a direct result of ingesting water containing this chemical. Similarly,
EPA estimates that ingesting water containing 3.0 µg/L would result
in not greater than a one-in-hundred thousand increased chance of developing
cancer, and water containing 30 µg/L would result in not greater
than a one-in-ten thousand increased chance of developing cancer. For
a detailed discussion of confidence in the potency estimates, please
see IRIS. (2)

Health Data from Inhalation Exposure

ACGIH TLV--American Conference of Governmental and Industrial
Hygienists' threshold limit value expressed as a time-weighted average;
the concentration of a substance to which most workers can be exposed
without adverse effects. LC50 (Lethal Concentration50)--A calculated
concentration of a chemical in air to which exposure for a specific length
of time is expected to cause death in 50% of a defined experimental animal
population. NIOSH IDLH -- National Institute of Occupational Safety and Health's
immediately dangerous to life or health concentration; NIOSH recommended
exposure limit to ensure that a worker can escape from an exposure condition
that is likely to cause death or immediate or delayed permanent adverse
health effects or prevent escape from the environment. NIOSH REL--NIOSH's recommended exposure limit; NIOSH-recommended
exposure limit for an 8- or 10-h time-weighted-average exposure and/or
ceiling. OSHA PEL--Occupational Safety and Health Administration's permissible
exposure limit expressed as a time-weighted average; the concentration
of a substance to which most workers can be exposed without adverse effect
averaged over a normal 8-h workday or a 40-h workweek.

The health and regulatory values cited in this factsheet were obtained
in December 1999.aHealth numbers are toxicological numbers
from animal testing or risk assessment values developed by EPA. bRegulatory numbers are values that have been
incorporated in Government regulations, while advisory numbers are nonregulatory
values provided by the Government or other groups as advice. OSHA numbers
are regulatory, whereas NIOSH and ACGIH numbers are advisory.

National Institute for Occupational Safety and
Health (NIOSH). Pocket
Guide to Chemical Hazards. U.S. Department of Health and
Human Services, Public Health Service, Centers for Disease Control and
Prevention. Cincinnati, OH. 1997.